The present invention relates to clock input buffers, and more particularly, to a clock input buffer that can automatically configure itself to receive high-voltage single-ended and low-voltage differential clock signals.
As integrated circuit transistors have shrunk in size, the thickness of the gate oxide used in the transistor has also decreased. In some advanced transistors, the thickness of the gate oxide is less than 50 angstroms. With a thin gate oxide, it is difficult for the transistor to accept high-voltage inputs. One common type of high-voltage input is a high-voltage single-ended clock signal. To ease the high-voltage problem, the trend is to use a low-voltage differential clock signal. This relaxes the amount of stress on the gate oxide for these new semiconductor devices.
However, there is still a demand for newer integrated circuits to be compatible with older integrated circuits that use a high-voltage single-ended clock signal. In other words, components that utilize these thin gate oxide semiconductor devices must nevertheless be able to handle both the low-voltage differential clock inputs and high-voltage single-ended clock inputs.